Up to now, in a current feedback control of a brushless motor, a technique in which a current command limit value is corrected so as not to saturate a voltage, and an abnormal noise or vibration of the motor is suppressed has been known.
For example, in the motor control device disclosed in Patent Literature 1, a voltage saturation is calculated according to a duty value of a PWM, and the current command limit value to achieve the duty of 100% is calculated on the basis of the voltage saturation, whereby the current command value is suppressed to prevent the saturation of the voltage.
In the device of Patent Literature 1, under the assumption that there is a proportional relationship between a motor terminal voltage and a duty value of the PWM, the voltage saturation is obtained according to the duty value. However, when three-phase modulation or two-phase modulation is performed in the generation of a PWM signal to be output to an inverter, because the duty value has no proportional relationship with an actual motor terminal voltage, a current limit cannot be performed with the use of the device of Patent Literature 1.
[Patent Literature 1] JP-2008-79387 A (corresponding to US 2008/0069547)